Together prenatal and postpartum depression affect 15% of pregnancies annually, and may compromise the mother's psychological well-being as well as the health and development of her infant and family. Most studies examining predictive factors for prenatal and postpartum depression have focused on demographic and psychosocial characteristics, but few have examined the role of modifiable behavioral factors such as diet. Adequate nutritional status is a necessary precursor for normal brain function and may be associated with depression. Omega-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), are important in neural tissues and affect receptor function, neurotransmitter uptake, and signal transmission. Higher intake of fish (the main dietary source of elongated omega-3 PUFAs) and of omega-3 PUFAs have been associated with lower risk of major depression. Previous studies among populations with higher dietary fish intake than United States women have suggested that there may be an inverse relation between fish and omega-3 PUFA intake and postpartum depression. To our knowledge, no study has examined the relation between omega-3 PUFA intake and prenatal depression. We will use data from a prospective cohort study of 1,662 mothers, Project Viva, to examine the following hypotheses: a) Higher maternal blood levels of omega-3 PUFAs during pregnancy are associated with lower risk of prenatal and postpartum depression. b) Higher dietary fish and omega-3 PUFA intake during pregnancy are associated with lower risk of prenatal depression and postpartum depression. c) Higher dietary fish and omega-3 PUFA intake during the postpartum period are associated with lower risk of postpartum depression. This project will take advantage of the wealth of data already collected by Project Viva, including stored maternal blood samples, validated prenatal dietary assessment, and detailed information about a number of covariates. Dietary intake of specific nutrients is a modifiable behavior that is well suited for interventions. Our study will shed further light in evaluating whether intake of omega-3 PUFA could be a cost-effective method of preventing prenatal and postpartum depression. [unreadable] [unreadable] [unreadable]